Background and Aim: Hamstring muscles are biarticular muscles, which conducted to pelvic and knee. Shortness of hamstring muscles can influence on the upper and lower joints of its attachment .With respect of the high prevalence of shortness of  these muscles, accurate assessment of these muscles is important. There are many tests for assessment of hamstring muscles length During using the straight leg raise (SLR) test, pelvic rotation can contribute to the angle of SLR, while pelvic movement in passive knee extension (PKE) is limited. This study was designed to measure the relationship between two alternative tests in order to use of simple and accurate PKE test for measuring of hamstring length.

Material & Method: 3308 healthy girls (3-17 years) were tested, and hamstring length were determined with using of two tests (SLR and PKE) for both side of lower limbs and measured of active SLR and popliteal angle (PA) with goniometer.

Conclusion: Results demonstrated relationship between two tests, in all of ages and both side. SLR and PKE tests can use for assessing of hamstring muscles shortness, but PKE test may be a useful alternative in comparison with activeSLR for providing an indication of hamstring muscle length.